DES与3DES 加解密实例（c++）

###DES原理：
DES算法是一种对称密码算法，也是一种分组加密的算法，以64位分组对数
据加密的，其密钥长度为64位，密钥事实上是56位参与DES运算（第8、16、24、
32、40、48、56、64位是校验位，使得每个密钥都有奇数个1），分组后的明文组和
56位的密钥按位替代或交换的方法形成密文组。
DES算法的主要流程如下图所示。

1、 IP置换
IP置换目的是将输入的64位数据块按位重新组合，并把输出分为L0、R0两部分，
每部分各长32位

2、密码置换
DES的密钥由64位减至56位，每个字节的第8位作为奇偶校验位。产生的56位
密钥。在DES的每一轮中，从56位密钥循环左移再置换产生出不同的48位子密钥。
总共16轮，所以有16个子密钥。

4、E扩展置换
扩展置置换目标是IP置换后获得的右半部分R0，将32位输入扩展为48位(分为4
位×8组)输出。
扩展置换目的有两个：生成与密钥相同长度的数据以进行异或运算；提供更长的结
果，在后续的替代运算中可以进行压缩。

5、S盒代替
压缩后的密钥与扩展分组异或以后得到48位的数据，将这个数据送人S盒，进行替
代运算。替代由8个不同的S盒完成，每个S盒有6位输入4位输出。48位输入分
为8个6位的分组，一个分组对应一个S盒，对应的S盒对各组进行代替操作。

5、 P盒置换
S盒代替运算的32位输出按照P盒进行置换。该置换把输入的每位映射到输出位，
任何一位不能被映射两次，也不能被略去。

6、 IP-1末置换
末置换是初始置换的逆过程，DES最后一轮后，左、右两半部分并未进行交换，而是两部分合并形成一个分组做为末置换的输入

本代码实现了mp3加密过程，可以按照文件自行修改

#include <iostream> #include <stdio.h> #include "memory.h" #include <time.h> #include <stdlib.h>  #define PLAIN_FILE_OPEN_ERROR -1 #define KEY_FILE_OPEN_ERROR -2 #define CIPHER_FILE_OPEN_ERROR -3 #define OK 1  ///定义数据类型 typedef char type; using namespace std; class Treble_DES {     ///初始置换表IP     int IP[64] = {  57,49,41,33,25,17,9,1,                     59,51,43,35,27,19,11,3,                     61,53,45,37,29,21,13,5,                     63,55,47,39,31,23,15,7,                     56,48,40,32,24,16,8,0,                     58,50,42,34,26,18,10,2,                     60,52,44,36,28,20,12,4,                     62,54,46,38,30,22,14,6};      ///逆初始置换表IP^-1     int IP_1[64] = {39,7,47,15,55,23,63,31,                38,6,46,14,54,22,62,30,                37,5,45,13,53,21,61,29,                36,4,44,12,52,20,60,28,                35,3,43,11,51,19,59,27,                34,2,42,10,50,18,58,26,                33,1,41,9,49,17,57,25,                32,0,40,8,48,16,56,24};      ///扩充置换表E     int E[48] = {31, 0, 1, 2, 3, 4,                 3, 4, 5, 6, 7, 8,                 7, 8,9,10,11,12,                 11,12,13,14,15,16,                 15,16,17,18,19,20,                 19,20,21,22,23,24,                 23,24,25,26,27,28,                 27,28,29,30,31, 0};      //置换函数P     int P[32] = {15,6,19,20,28,11,27,16,                       0,14,22,25,4,17,30,9,                       1,7,23,13,31,26,2,8,                       18,12,29,5,21,10,3,24};      //S盒     int S[8][4][16] =//S1                 {{{14,4,13,1,2,15,11,8,3,10,6,12,5,9,0,7},                   {0,15,7,4,14,2,13,1,10,6,12,11,9,5,3,8},                     {4,1,14,8,13,6,2,11,15,12,9,7,3,10,5,0},                     {15,12,8,2,4,9,1,7,5,11,3,14,10,0,6,13}},                     //S2                   {{15,1,8,14,6,11,3,4,9,7,2,13,12,0,5,10},                   {3,13,4,7,15,2,8,14,12,0,1,10,6,9,11,5},                   {0,14,7,11,10,4,13,1,5,8,12,6,9,3,2,15},                   {13,8,10,1,3,15,4,2,11,6,7,12,0,5,14,9}},                   //S3                   {{10,0,9,14,6,3,15,5,1,13,12,7,11,4,2,8},                   {13,7,0,9,3,4,6,10,2,8,5,14,12,11,15,1},                     {13,6,4,9,8,15,3,0,11,1,2,12,5,10,14,7},                   {1,10,13,0,6,9,8,7,4,15,14,3,11,5,2,12}},                   //S4                   {{7,13,14,3,0,6,9,10,1,2,8,5,11,12,4,15},                   {13,8,11,5,6,15,0,3,4,7,2,12,1,10,14,9},                   {10,6,9,0,12,11,7,13,15,1,3,14,5,2,8,4},                   {3,15,0,6,10,1,13,8,9,4,5,11,12,7,2,14}},                   //S5                   {{2,12,4,1,7,10,11,6,8,5,3,15,13,0,14,9},                   {14,11,2,12,4,7,13,1,5,0,15,10,3,9,8,6},                   {4,2,1,11,10,13,7,8,15,9,12,5,6,3,0,14},                   {11,8,12,7,1,14,2,13,6,15,0,9,10,4,5,3}},                   //S6                   {{12,1,10,15,9,2,6,8,0,13,3,4,14,7,5,11},                   {10,15,4,2,7,12,9,5,6,1,13,14,0,11,3,8},                   {9,14,15,5,2,8,12,3,7,0,4,10,1,13,11,6},                   {4,3,2,12,9,5,15,10,11,14,1,7,6,0,8,13}},                   //S7                   {{4,11,2,14,15,0,8,13,3,12,9,7,5,10,6,1},                   {13,0,11,7,4,9,1,10,14,3,5,12,2,15,8,6},                   {1,4,11,13,12,3,7,14,10,15,6,8,0,5,9,2},                   {6,11,13,8,1,4,10,7,9,5,0,15,14,2,3,12}},                   //S8                   {{13,2,8,4,6,15,11,1,10,9,3,14,5,0,12,7},                   {1,15,13,8,10,3,7,4,12,5,6,11,0,14,9,2},                   {7,11,4,1,9,12,14,2,0,6,10,13,15,3,5,8},                   {2,1,14,7,4,10,8,13,15,12,9,0,3,5,6,11}}};     //置换选择1     int PC_1[56] = {56,48,40,32,24,16,8,                   0,57,49,41,33,25,17,                   9,1,58,50,42,34,26,                   18,10,2,59,51,43,35,                   62,54,46,38,30,22,14,                   6,61,53,45,37,29,21,                   13,5,60,52,44,36,28,                   20,12,4,27,19,11,3};      //置换选择2     int PC_2[48] = {13,16,10,23,0,4,2,27,                   14,5,20,9,22,18,11,3,                   25,7,15,6,26,19,12,1,                   40,51,30,36,46,54,29,39,                   50,44,32,46,43,48,38,55,                   33,52,45,41,49,35,28,31};      //对左移次数的规定     int left[16] = {1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};      ///字节转换成二进制     int ByteToBit(type ch, type bit[8]){         int cnt;         for(cnt = 0;cnt < 8; cnt++){             *(bit+cnt) = (ch>>cnt)&1;         }         return 0;     }      ///二进制转换成字节     int BitToByte(type bit[8],type *ch){         int cnt;         for(cnt = 0;cnt < 8; cnt++){             *ch |= *(bit + cnt)<<cnt;         }         return 0;     }      ///将长度为8的字符串转为二进制位串     int Char8ToBit64(type ch[8],type bit[64]){         int cnt;         for(cnt = 0; cnt < 8; cnt++){             ByteToBit(*(ch+cnt),bit+(cnt<<3));         }         return 0;     }      ///将二进制位串转为长度为8的字符串     int Bit64ToChar8(type bit[64],type ch[8]){         int cnt;         memset(ch,0,8);         for(cnt = 0; cnt < 8; cnt++){             BitToByte(bit+(cnt<<3),ch+cnt);         }         return 0;     }      ///生成子密钥     int DES_MakeSubKeys(type key[64],type subKeys[16][48]){         type temp[56];         int cnt;         DES_PC1_Transform(key,temp);//PC1置换         for(cnt = 0; cnt < 16; cnt++){//16轮跌代，产生16个子密钥             DES_ROL(temp,left[cnt]);//循环左移             DES_PC2_Transform(temp,subKeys[cnt]);//PC2置换，产生子密钥         }         return 0;     }      ///密钥置换pc1     int DES_PC1_Transform(type key[64], type tempbts[56]){         int cnt;         for(cnt = 0; cnt < 56; cnt++){             tempbts[cnt] = key[PC_1[cnt]];         }         return 0;     }      ///密钥置换pc2     int DES_PC2_Transform(type key[56], type tempbts[48]){         int cnt;         for(cnt = 0; cnt < 48; cnt++){             tempbts[cnt] = key[PC_2[cnt]];         }         return 0;     }      ///循环左移     int DES_ROL(type data[56], int time){         type temp[56];          //保存将要循环移动到右边的位         memcpy(temp,data,time);         memcpy(temp+time,data+28,time);          //前28位移动         memcpy(data,data+time,28-time);         memcpy(data+28-time,temp,time);          //后28位移动         memcpy(data+28,data+28+time,28-time);         memcpy(data+56-time,temp+time,time);          return 0;     }      ///IP置换     int DES_IP_Transform(type data[64]){         int cnt;         type temp[64];         for(cnt = 0; cnt < 64; cnt++){             temp[cnt] = data[IP[cnt]];         }         memcpy(data,temp,64);         return 0;     }      ///IP逆置换     int DES_IP_1_Transform(type data[64]){         int cnt;         type temp[64];         for(cnt = 0; cnt < 64; cnt++){             temp[cnt] = data[IP_1[cnt]];         }         memcpy(data,temp,64);         return 0;     }      ///扩展置换     int DES_E_Transform(type data[48]){         int cnt;         type temp[48];         for(cnt = 0; cnt < 48; cnt++){             temp[cnt] = data[E[cnt]];         }         memcpy(data,temp,48);         return 0;     }      ///P置换     int DES_P_Transform(type data[32]){         int cnt;         type temp[32];         for(cnt = 0; cnt < 32; cnt++){             temp[cnt] = data[P[cnt]];         }         memcpy(data,temp,32);         return 0;     }      ///异或     int DES_XOR(type R[48], type L[48] ,int count){         int cnt;         for(cnt = 0; cnt < count; cnt++){             R[cnt] ^= L[cnt];         }         return 0;     }      ///S盒置换     int DES_SBOX(type data[48]){         int cnt;         int line,row,output;         int cur1,cur2;         for(cnt = 0; cnt < 8; cnt++){             cur1 = cnt*6;             cur2 = cnt<<2;              //计算在S盒中的行与列             line = (data[cur1]<<1) + data[cur1+5];             row = (data[cur1+1]<<3) + (data[cur1+2]<<2)                 + (data[cur1+3]<<1) + data[cur1+4];             output = S[cnt][line][row];              //化为2进制             data[cur2] = (output&0X08)>>3;             data[cur2+1] = (output&0X04)>>2;             data[cur2+2] = (output&0X02)>>1;             data[cur2+3] = output&0x01;         }         return 0;     }      ///交换     int DES_Swap(type left[32], type right[32]){         type temp[32];         memcpy(temp,left,32);         memcpy(left,right,32);         memcpy(right,temp,32);         return 0;     }      ///加密单个分组     int DES_EncryptBlock(type plainBlock[8], type subKeys[16][48], type cipherBlock[8]){         type plainBits[64];         type copyRight[48];         int cnt;          Char8ToBit64(plainBlock,plainBits);         //初始置换（IP置换）         DES_IP_Transform(plainBits);          //16轮迭代         for(cnt = 0; cnt < 16; cnt++){             memcpy(copyRight,plainBits+32,32);             //将右半部分进行扩展置换，从32位扩展到48位             DES_E_Transform(copyRight);             //将右半部分与子密钥进行异或操作             DES_XOR(copyRight,subKeys[cnt],48);             //异或结果进入S盒，输出32位结果             DES_SBOX(copyRight);             //P置换             DES_P_Transform(copyRight);             //将明文左半部分与右半部分进行异或             DES_XOR(plainBits,copyRight,32);             if(cnt != 15){                 //最终完成左右部的交换                 DES_Swap(plainBits,plainBits+32);             }         }         //逆初始置换（IP^1置换）         DES_IP_1_Transform(plainBits);         Bit64ToChar8(plainBits,cipherBlock);         return 0;     }      ///解密单个分组     int DES_DecryptBlock(type cipherBlock[8], type subKeys[16][48],type plainBlock[8]){         type cipherBits[64];         type copyRight[48];         int cnt;          Char8ToBit64(cipherBlock,cipherBits);         //初始置换（IP置换）         DES_IP_Transform(cipherBits);          //16轮迭代         for(cnt = 15; cnt >= 0; cnt--){             memcpy(copyRight,cipherBits+32,32);             //将右半部分进行扩展置换，从32位扩展到48位             DES_E_Transform(copyRight);             //将右半部分与子密钥进行异或操作             DES_XOR(copyRight,subKeys[cnt],48);             //异或结果进入S盒，输出32位结果             DES_SBOX(copyRight);             //P置换             DES_P_Transform(copyRight);             //将明文左半部分与右半部分进行异或             DES_XOR(cipherBits,copyRight,32);             if(cnt != 0){                 //最终完成左右部的交换                 DES_Swap(cipherBits,cipherBits+32);             }         }         //逆初始置换（IP^1置换）         DES_IP_1_Transform(cipherBits);         Bit64ToChar8(cipherBits,plainBlock);         return 0;     }      //加密文件     public: int treble_DES_Encrypt(char *plainFile, type *key_1,type *key_2,type *key_3,char *cipherFile){         FILE *plain, *cipher;         int count;         long fileLen;         type plainBlock[8],cipherBlock1[8],cipherBlock2[8],cipherBlock3[8];         type Key1[64];         type Key2[64];         type Key3[64];         type subKeys1[16][48];         type subKeys2[16][48];         type subKeys3[16][48];          if((cipher = fopen(cipherFile,"wb")) == NULL){             return CIPHER_FILE_OPEN_ERROR;         }         if((plain = fopen(plainFile,"rb")) == NULL){             return PLAIN_FILE_OPEN_ERROR;         }         //设置密钥         //将密钥转换为二进制流         Char8ToBit64(key_1,Key1);         Char8ToBit64(key_2,Key2);         Char8ToBit64(key_3,Key3);         //生成子密钥         DES_MakeSubKeys(Key1,subKeys1);         DES_MakeSubKeys(Key2,subKeys2);         DES_MakeSubKeys(Key3,subKeys3);          //如果文件非空         while(!feof(plain)){             //每次读8个字节，并返回成功读取的字节数             if((count = fread(plainBlock,sizeof(char),8,plain)) == 8){                 //3DES加密单组文件                 DES_EncryptBlock(plainBlock,subKeys1,cipherBlock1);                 DES_DecryptBlock(cipherBlock1,subKeys2,cipherBlock2);                 DES_EncryptBlock(cipherBlock2,subKeys3,cipherBlock3);                 //写入                 fwrite(cipherBlock3,sizeof(char),8,cipher);             }         }         //补充最后一组         if(count){             //填充             memset(plainBlock + count,'\0',7 - count);             //最后一个字符保存包括最后一个字符在内的所填充的字符数量             plainBlock[7] = 8 - count;             //加密单个分组             DES_EncryptBlock(plainBlock,subKeys1,cipherBlock1);             DES_DecryptBlock(cipherBlock1,subKeys2,cipherBlock2);             DES_EncryptBlock(cipherBlock2,subKeys3,cipherBlock3);             //写入文件             fwrite(cipherBlock3,sizeof(char),8,cipher);         }         fclose(plain);         fclose(cipher);         return OK;     }      //解密文件    public: int treble_DES_Decrypt(char *cipherFile, type *key_1,type *key_2,type *key_3,char *plainFile){         FILE *plain, *cipher;         int count,times = 0;         long fileLen;         type plainBlock1[8],plainBlock2[8],plainBlock3[8],cipherBlock[8];         type Key1[64];         type Key2[64];         type Key3[64];         type subKeys1[16][48];         type subKeys2[16][48];         type subKeys3[16][48];          if((cipher = fopen(cipherFile,"rb")) == NULL){             return CIPHER_FILE_OPEN_ERROR;         }         if((plain = fopen(plainFile,"wb")) == NULL){             return PLAIN_FILE_OPEN_ERROR;         }          //将密钥转换为二进制流         Char8ToBit64(key_1,Key1);         Char8ToBit64(key_2,Key2);         Char8ToBit64(key_3,Key3);         //生成子密钥         DES_MakeSubKeys(Key1,subKeys1);         DES_MakeSubKeys(Key2,subKeys2);         DES_MakeSubKeys(Key3,subKeys3);          //取文件长度         fseek(cipher,0,SEEK_END);   //将文件指针置尾         fileLen = ftell(cipher);    //取文件指针当前位置         rewind(cipher);             //将文件指针重指向文件头         while(1){             //密文的字节数一定是8的整数倍             fread(cipherBlock,sizeof(char),8,cipher);             //3DES解密             DES_DecryptBlock(cipherBlock,subKeys3,plainBlock1);             DES_EncryptBlock(plainBlock1,subKeys2,plainBlock2);             DES_DecryptBlock(plainBlock2,subKeys1,plainBlock3);              times += 8;             if(times < fileLen){                 fwrite(plainBlock3,sizeof(char),8,plain);             }             else{                 break;             }         }         //判断末尾是否被填充         if(plainBlock3[7] < 8){             for(count = 8 - plainBlock3[7]; count < 7; count++){                 if(plainBlock3[count] != '\0'){                 //3des                 DES_DecryptBlock(cipherBlock,subKeys3,plainBlock1);                 DES_EncryptBlock(plainBlock1,subKeys2,plainBlock2);                 DES_DecryptBlock(plainBlock2,subKeys1,plainBlock3);                 break;                 }             }         }         if(count == 7){//有填充             fwrite(plainBlock3,sizeof(char),8 - plainBlock3[7],plain);         }         else{//无填充             fwrite(plainBlock3,sizeof(char),8,plain);         }          fclose(plain);         fclose(cipher);         return OK;     }  };   int main() {     type key_1[8] =  {'1','1','2','2','3','3','4','4'};     type key_2[8] =  {'a','b','c','d','e','f','g','h'};     type key_3[8] =  {'1','2','3','4','5','6','7','8'};     Treble_DES d;     cout<<"开始加密"<<endl;     cout<<d.treble_DES_Encrypt("1.mp3",key_1,key_2,key_3,"加密.txt");     cout<<"加密结束，开始解密"<<endl;     cout<<d.treble_DES_Decrypt("加密.txt",key_1,key_2,key_3,"temp.mp3");     cout<<"解密完成"<<endl;     getchar();      return 0; }

来源：CSDN

作者：武倔

链接：https://blog.csdn.net/blowfire123/article/details/78566312

标签

des

对称密钥